School yard biodiversity determines short-term recovery of disturbed skin microbiota in children

The planting and conservation of biodiverse habitat in urban contexts has been proposed as a public health intervention aimed at reducing the prevalence of non-communicable diseases via microbiome rewilding (Mills et al. 2017; Mills et al. 2019). However, our understanding of the effect of urban biodiversity interventions on the human microbiota remains limited, especially on the skin (Hui et al. 2019; Roslund et al. 2020) and in the context of permanent green spaces (Lehtimaki et al. 2018; Selway et al. 2020). Here, we test the short-term response of experimentally disturbed bacterial communities on the skin of healthy children exposed to different school environments - either a classroom, a sports field, or a biodiverse forest - to understand how exposures to different types of biodiversity may influence skin microbiota. Children exposed to the forest had significantly increased skin microbiota diversity when compared to pre-exposure, an effect that increased over three days suggesting long-term effects. The microbiota on children exposed to the forest had the largest structural and compositional community change compared to children exposed to sports fields, which in turn was larger than those who remained in classrooms. Children exposed to sports fields and forests also acquired new core bacteria after exposure to green spaces, potentially buffering against disturbances to the skin microbiotas diversity, while individuals who remained in the classroom lost microbes throughout the experiment. Overall, we conclude that urban green spaces can have an enriching influence on the diversity of skin microbiota, including core members shared between all children. These findings have important implications for the design and construction of new school yards and public spaces with respect to biodiversity, health, and human microbiota.